This study aimed to investigate impacts of the combination of Gluconacetobacter diazotrophicus with reduced nitrogen inputs on N2O emissions in paddy rice in the Mekong Delta region, Vietnam. The field experiment was arranged in a split-plot design, with method of inoculating rice seeds with G. diazotrophicus as the main-plot factor and N fertilizer rates as the subplot factor. Rice seeds were inoculated with G. diazotrophicus (Gd) and non-inoculated with G. diazotrophicus (Go). The rates of N fertilizer included N0, N50, N75, and N100 are received 0, 50, 75, and 100 kg N ha–1, respectively. The results showed that the combination of G. diazotrophicus with N fertilizer at rates of 50–75 kg ha–1 show a trend toward reducing N2O emissions by 13.5–19.2%, equivalent to a reduction of 191–259 kg CO2eq ha–1crop–1 in both cropping seasons. It is recommended that the further long-term studies in combination with N fertilizer application to comprehensive determine effect of G. diazotrophicus bacteria on the mitigation of N2O emissions, GWP, and GHGI in the paddy rice system in the Vietnamese Mekong Delta region.